The play is about death and dying, but it is also about grief, and our unavoidably clumsy way of dealing with it. There is never any grace in grief.
Susannah Mars once again plays a mother who has lost a child, a role she has played twice before in Artists Rep productions, "Rabbit Hole" and "Next to Normal," and it is a role she crushes every time, in such a way as to make it look effortless. Michael Mendelson plays a terminally ill man, and while the role does have room in it for him to be a bit of a goofball free-spirit, his raging speech at the end is a departure for the character, and if memory serves, for Mendelson himself.
Michael Fisher-Welsh has the thankless job of playing the stiff and boring grieving father, a man who has had every ounce of joy sucked from him. I say "thankless" because we spend much of the play not liking him, so the challenge is to imbue him with a dwindling spark of humanity, doused almost completely by sadness. Fisher-Welsh succeeds, and the audience owes him thanks.
I've been trying not to use "gut-wrenching" because it is a cliche, but perhaps I'll be granted a pass if I admit that the aforementioned last scene with Mendelson made me nauseated. You have been warned.